Prosthetic hook with dual spring load



Oct. 30, 1951 G. M. MOTIS PROSTHETIC HOOK WITH DUAL SPRING LOAD 2 SHEETSSHEET 1 Filed Dec. 12, 1950 v Z 6 0 Z Q 4 mW v I. 1 f 6 3 U G J 64.56977! Mar/.5

INVENTOR.

47'7'0PN5Y.

Oct. 30, 1951 M6115 2,573,351 PROSTHETIC HOOK WITH DUAL SPRING LOAD Filed Dc. 12, 1950 2 SHEETS-SHEET 2 6/465??- M MOT/J INVENTOR.

Patented Oct. 30, 1951 I PROSTHETIC HOOK'WITH DUAL SPRINGLOAD W. 1

Gilbert M. Motis, Sherman oaks, Ca]if.,'assig1iorf to Northrop Aircraft, Inc., Hawthorne',"0alif.,' a corporation of California Application December 12, 195 0,,Serial No. 200,440

8 Claims.

. Thepresent invention relates to utility hooks for artificial arms, and more particularly, to the class of hook wherein a movable finger is closed against a cooperating finger by the action of a spring, and is voluntarily pulled open against the spring pressure by a control force exerted by the amputee. Hooks of this type are generally referred to as voluntary opening or pull-toopen, hooks, and heretofore, the spring load on the movable finger has been obtained by means of relatively heavy rubber bands which are wrapped around the stationary and movable fingers near the basal ends thereof.

The amount of spring load on the movable finger of these prior hooks is determined by the size, weight, and number of rubber bands used, and the usual practice has been to use the hooks normally with only one or two rubber bands, which exert a closing force on the movable finger of from two to four pounds. When a particular task required a stronger closing force on the hook, the amputee would wrap additionalrubber bands around the hook fingers; and likewise, when it was desired to use a lighter spring load, one or more of the rubber bands would be removed. The operation of adding rubber bandsto or removing them from the hook is slow and awkward, particularly for bilateral amputees, and there has long been need for a faster, more convenient way of changing the spring load on the hook to accommodate the. tension to suit the task. The primary object of the present invention, therefore, is to provide a hook of the class described wherein means is provided for quickly and easily changing the spring tension on the movable finger.

Another object of the invention is to provide a prosthetic hook having a pivoted; movable finger which is normally urged toward the closed position with a light spring load, andfwherein means is provided for substantially increasing the spring load on the said finger by merely shifting a slidable selector button on the hook.

These objects are attained in the present invention by the provision of a pair of torsion springs, one of which is attached to the movable finger at all times to exert a light spring tension thereon, and the other being normally disconnected from the finger. 7 A slidable selector button on the hook is operable to shift .a locking pin in the base of the movable finger into engagement with the other spring, thereby Q0111 necting the latter to the movable finger so that the combined force of both springs is exerted thereon. By'this arrangement, thespring load (Cl; 3&12)

on the movable finger can be changed quickly and easily from light to heavy or vice versa, without the inconvenience of adding rubber bands t6 the hook or removingfthem therefrom.

Still a further object of the invention is to provide a hook of the class described wherein the spring mechanism is entirely contained within an'outer'case that is smoothly rounded on all sides to eliminate corners and sharp edges which cause much damage to clothing.

The foregoing and other objects and advantages of the inventionwill become apparent to those skilled inthe art upon consideration of the .following detailed descriptionof the presently preferred embodiment thereof, reference being had to the accompanying drawings, wherein: "Figure 1 is a plan view of a hook embodying the principles of my invention;

Figure 2 is a side elevational view of the same;

Figure 3 is an enlarged cross-section, taken along the line 33' in Figure 1; I Figure 4 is an enlarged sectional at 4 4 in Figure l; and Figure 5 is an enlarged fragmentary view of the thumb, partially cut away to show the details of the selector button and locking pin.

In the drawings, the hook of the invention is designated in its entirety by the reference numeral l0, and is seen to comprise a body, or outer case II which contains the spring loading mechanism, and which supports the stationary load finger l2, movable load finger I 3, and thumb 14. The body H is preferably formed of aluminum alley or other light metal,- and comprises a generally circular, cup-shaped member l5 havinga cover plate 16 over the open end thereof. The member l5 has a bottom wall 20 and substantially cylindrical 1 side walls 2|, and projecting from the center of they bottom wall is a raised cylindrical boss 22. A tapped hole 23 is formed in the outer end of the boss at the axis thereof, and threaded into the said hole is a screw 24 which secures the cover plate l6 to the body member IS. The cover plate I6 is likewise formed with a raised, central boss 25 having a hole 26 drilled through the center thereof to pass the, screw 24. The boss 25 on the cover plate abuts against the boss 22 on'the. body member, and the two bosses are provided on their abutting ends with interlocking tongue and groove formations (not shown) which prevent relative rotation betweenthe cover plate l6 and body member I5.,

Projecting downwardly from the. side wall 2| at the bottom edge of the-body H is a threaded view, taken shank 35 which is adapted to be screwed into a socket provided therefor in the wrist end 3| of an artificial forearm member 32. At the opposite side of the body H i an outwardly projecting boss 33 having a, hole 34 drilled therein to receive the shank 35 of the stationary finger l2,

The shank 36 of the movable member 13 is inserted into a hole 40 drilled into a boss 4| formed on a rotatable spring case 42. A section of the cylindrical wall portion 2! is out out,

of the case to form a circumferential opening 48, and the movable finger boss 41 projects through this opening and movesalong the length thereof when the hook is opened. Each of the race 75 is opposed by a cup race 16 on the cover finger shanks and 36 is properly positioned within its respective socket hole and isheld against turning therein by a taper pin 43, which is driven through alined holes in the boss and in the shank.

--The spring case 42 is annular in shape, with acylindrical outer peripheral portion 44 and a cup shaped inner portion 45. Ball bearing cup races 45 and 41 are formed in opposite ends of the outer peripheral portion 44, and running in these races are ball bearings and 5|, which provide anti-friction bearing support for the spring case 42. Opposite the cup race 41 is a cone race 52 which is formed in a raised annular portion 53 of the cover l6, and provides the necessary second race for the ball bearings 5|. The cup-shaped portion 45 of the spring case 42 extends into alcavity 54 surrounded by the annular portion 53 of the cover, and is apertured topass theboss 25. Nested within the cup-shaped portion 45 is a torsion spring 56 of the spirally wound, fiat ribbon type, such as is used in clock works. The inner end of the spring bent radially inward to form an anchor tab 50 (Figure 4) which is inserted into a slot 51 in the boss 25, and the outer end of the spring is attached by a rivet 62 to the spring case 42. The direction of winding of the spring 55 is such'that the spring exerts a closing tensionpn themovable finger l3, urging the latter in the clockwise direction in Figure 1, toward the stationary finger l2. The spring 56 is lightly pro-loaded at the time of assembly, and exerts a spring load of from 2 to 4 pounds on the movable finger, as measured at the tip end thereof.

Qisp osed, within the cavity of the cup-shaped member i5 alongside the spring case 42 and rotatable coaxially therewith is another cup- Shapedspring case 53 which contains a second torsion spring 54-. This second spring is likewise bent radially inwardly at its inner end to form an anchor tab 55 (Figure 4) that is inserted into a slot 56 in the boss 22 and its outer end is, attached by a rivet 15 to the spring case 63. Spring 54 is also wound to produce a clockwise (Figure l) torque on the spring case 53, and, may bepre-loaded so that when the spring case 513 is'connected to the movable finger, the. latter is spring loaded to any desired tension under the combined force of the two prings 55 and 54.

The preloading of spring 64 is accomplished by means of a limit. stop pin H which is secured within a hole in the bottom 20 of member 15,

and passes through an arcuate slot 12 in the side of spring case 6 3. Sprin case 63 is thus limited in its clockwise (Figure 1) rotation by the engagement of the end of the slot 12 with the pin H, and the spring 54 is thereby prevented from unwinding beyond the limited po- 20. lhe three rows of ball bearings 50, 5| and 13 provide for relatively free rotation of the spring case 42 with respect to both the body H and the other spring case 53, or simultaneous rotation of "the two interlocked spring cases 42, 63

.with respect to the body ll.

The selector means for optionally locking the spring case 53 to spring case 42 will now be described and, as shown in the drawings, comprises a locking pin so which is slidable within a bore Bl between locked and unlocked positions." The bore 8| is formed within a thumbextension 82 of the movable finger boss 4|, and extends in a direction radial to the pivot axis of the finger. Bore 8i and pin are also offset slightly to one side of center of the thumb-extension 82, as shown in Figure 4, so that the inner end of pin is engageable in a hole 83 in spring case 63, and at its outer end, bore 8! opens into a larger diameter bore 84, which is centered in the thumb-extension 82.

Slidable axially within the bore 84 is a cylindrical body 85 which is eccentric with respect to the locking pinBil and formed integrally therewith. The cylinder 85 is drilled diametrically at B5, and inserted into the hole thus formed is a stem having a button 9| on the outer end thereof. The stem 98 extends through and is slidable within a slot 92 in the thumb-extension 82, and is secured within the hole 86 by a set screw 93, which is threaded into a tapped hole in the outer end of the cylinder 85. The cylindrical body 85 has two axially spaced, circumferentially extending'grooves 94 and 95 formed therein (Figure 4) which are engageable by a spring-pressed detent 96.

The detent 95 consists of a cylindrical plunger 91 which is slidable within a bore 98 that intersects the bore 84 at right angles thereto. A spring 99, backed up by a set screw I00, presses the plunger 9! against the cylindrical body 85 of the locking pin. A bullet-shaped nose on the end of the plunger 9? drops into the grooves 94, 95'when the locking pin is in one or the other of its two positions. The detent 55 thus holds the locking pin 80 in either of its positions, and at'the same time is yieldable' when sufiicient pressure is applied to the button 9! to permit the pin to be shifted to the other position.

Mounted on the outer end of the thumb-extension 82 is athumb member H36, the outer extremi'ty of which extendslaterally and rearwardly away iromthe points of the fingers l2, 13. A spherical socket ")1 is provided in the thumb tOBQwith a slot I58 (Figure 4) extending through one side thereof. Seated within the socket I 01 is a ball fitting I89 which is swaged onto the end of a Bowden cable control wire I i0, and the other end ofthe wire is attached to the usual shoulder harnessin'any suitable manner. The slot I08 at one-side of the thumb member enables the ball lflll to be seated in the spherical socket I07 without removing the ball from the end or the control wire.

The thumb I06 may be attached to the thumb extension 82 in any suitable manner, and is illustratively shown as having a stem l l l which is inserted down into the bore 84, and is properly positioned and securely held therein by a taper pin H2, which is driven through alined holes in the thumb-extension 82 and in the stem HI.

The operation of my invention is as follows: Normally, the movable finger i3 is spring-loaded with a relatively light tension so that the hook can be opened with a minimum of muscular effort. Also, for the majority of light tasks, a closing force of only 2 to 4 pounds at the tip end of the movable finger I3 is entirely adequate, and a heavier force might crush or otherwise damage any fragile article grasped with the hook. For this light spring tension, the button 9! is shifted outwardly along the slot 92 so that the pin 83 is retracted from hole 83 of the spring case 53. In this condition, the movable finger I3 is urged toward the closed position solely by the tension of spring 56.

When it is desired to apply a stronger spring load to the movable finger, the button Si is shifted inwardly along the slot 92, thereby projecting the end of locking pin 39 into hole 83. This has the effect of locking spring case 63 to spring case 42, and the movable finger I3 is then urged toward the closed position with the combined force of both springs. The movable finger l3 can thus be loaded with either a light spring tension or heavy spring tension by merely shifting the button 9| to its outer or inner position, respectively.

While I have shown and described in considerable detail what I believe to be the preferred form of my invention, it will be understood that various changes may be made in the shape and arrangement of the several parts thereof without departing from the broad scope of the invention, as defined in the appended claims.

I claim:

1. A prosthetic h-ook comprising a body, a finger mounted on said body for movement between closed and open positions, spring means urging said finger toward one of said positions, a second spring means normally disconnected from said finger, and selector means operable to connect said second spring means to said finger, whereby the tension of said second spring means is compounded with the tension of said firstnamed spring means to change the spring load on said finger.

2. A prosthetic hook comprising a body, a finger pivoted on said body for rotation between closed and open positions, a torsion spring connected to said finger to urge the same toward one of said positions, a second torsion spring normally disconnected from said finger, and selector means operable to connect said finger to said second torsion spring, whereby the tension of the latter is compounded with the tension of said first-named torsion spring to change the spring load on said finger.

3. A prosthetic hook comprising a body, a finger mounted on said body for movement between closed and open positions, spring means connected to said finger for exerting a predetermined amount of spring load thereon toward said closed position, a second spring means normally disconnected from said finger, and selector means operable to connect said second spring means to said finger, whereby the tension of said second spring means is added to the tension of said firstnamed spring means to increase the spring load on said finger.

4. A prosthetic hook comprising a body, a finger pivoted on said body for rotation between closed and open positions, a pair of springs, means connecting one of said springs to said finger for closing the latter with a light spring tension, and selector means for optionally connecting the other of said springs to said finger, whereby the combined force of said pair of springs is applied on the finger to close the latter with a heavy spring tension.

5. A prosthetic hook comprising a body, a finger pivoted on said body for rotation between closed and open positions, a pair of torsion springs arranged side by side within said case, one of said springs being constantly connected to said finger to move the same toward said closed position with a light spring tension, a rotatable spring case enclosing the other of said springs and attached thereto, and means for optionally connecting said finger to said spring case, whereby the force of said other spring is added to the force of said one spring to close said finger with a heavy spring tension.

6. A prosthetic hook comprising a body, a pair of spring cases supported for coaxial rotation on said body, a finger mounted on one of said cases and rotatable therewith between open and closed positions, a pair of springs attached one to each of said cases for urging the same in the fingerclosing direction, and means for optionally connecting said one case tothe other case, whereby the force of both springs can be applied to said finger to close the latter with a heavy spring ten- '7. A prosthetic hook comprising a body, a pair of spring cases supported for coaxial rotation on said body, a finger mounted on one of said cases and rotatable therewith between open and closed positions, a pair of springs attached one to each of said cases for urging the same in the fingerclosing direction, a connector pin slidable on said one spring case between positions in engagement with or disengaged from the other spring case, whereby said finger can be optionally connected with one or both of said spring cases to apply a light or heavy spring tension thereon.

8. A prosthetic hook comprising a body having a stationary finger mounted thereon, a pair of spring cases arranged side by side within said body and supported for coaxial rotation with respect thereto, a movable finger mounted on one of said cases and rotatable therewith between open and closed positions with respect to said stationary finger, a pair of torsion springs contained within said cases, each of said springs being attached to one of said cases for urging the same in the finger-closing direction, said one case having a portion overlying the periphery of the other case, and a pin slidably supported in said overlying portion of said one case for movement in a direction radial to the axis of rotation of said cases, said pin being engageable in a hole in the periphery of said other case to lock said cases together, whereby the force of both of said springs can be applied to said movable finger at the option of the wearer to close said movable finger with a heavy spring tension.

GILBERT M. MOTIS.

No references cited. 

